‘Stealth Omicron’ is now in the U.S.—but experts say so far it doesn’t seem more dangerous

Cases of the BA.2 sub-strain have been identified in Washington state, Texas and elsewhere. So far, according to Washington authorities, there are fewer than 100 confirmed cases in the country.

That’s a far cry from the situation in Denmark, where BA.2 now accounts for around 65% of new infections—a significant surge, given that Denmark is experiencing record case numbers of around 40,000 a day. In the U.K., health authorities said Friday that BA.2 was a “variant under investigation” that is accounting for a growing proportion of cases, with 426 now confirmed.

BA.2 is known as “stealth Omicron” because it lacks a particular mutation that makes BA.1—the type of Omicron that’s been spreading like wildfire over the last couple months—relatively easy to identify using PCR tests. (Contrary to some reports, the lack of this mutation does not mean BA.2 evades tests; it just makes it harder to correctly classify.)